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Some passages are designed to guard the reader against serious errors, where he risks falling; these passages are signposted in the margin by the sign ☡ ("dangerous bend")
Some passages are designed to guard the reader against serious errors, where he risks falling; these passages are signposted in the margin by the sign ☡ ("dangerous bend")
|source=Nicholas Bourbaki's description of the symbol in several textbooks<ref>See, for example, ''[http://books.google.com/books?id=VDGifaOQogcC&pg=SA1-PA5 Théorie des ensembles]'', p. I-8.</ref>
|source=Nicholas Bourbaki's description of the symbol in several textbooks<ref>See, for example, ''[http://books.google.com/books?id=VDGifaOQogcC&pg=SA1-PA5 Théorie des ensembles]'', p. I-8.</ref>
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[[File:Dangerous bend symbol.png|thumb|left|Knuth's "Dangerous Bend" sign]]
[[File:Dangerous bend symbol.png|thumb|left|Knuth's "Dangerous Bend" sign]]

Revision as of 06:35, 4 September 2011

Certains passages sont destinés à prémunir le lecteur contre des erreurs graves, où il risquerait de tomber; ces passages sont signalés en marge par le signe ☡ («tournant dangereux»)

Some passages are designed to guard the reader against serious errors, where he risks falling; these passages are signposted in the margin by the sign ☡ ("dangerous bend")

— Nicholas Bourbaki's description of the symbol in several textbooks[1]

Knuth's "Dangerous Bend" sign

The dangerous bend symbol ☡ (unicode number x02621) was created by the Nicolas Bourbaki group of mathematicians and appears in the margins of mathematics books written by the group. It resembles a road sign that indicates a "dangerous bend" in the road ahead, and is used to mark passages tricky on a first reading or with an especially difficult argument.[2]

Others have used variations of the symbol in their textbooks, and computer scientist Donald Knuth used a more realistic road-sign depiction in his Metafont and TeX systems.[3]

Typography

In the LaTeX typesetting system (version 3), the dangerous bend symbol can be written as:[4]

\begin{danger} ... \end{danger}
\begin{ddanger} ... \end{ddanger}.

References

  1. ^ See, for example, Théorie des ensembles, p. I-8.
  2. ^ Steven G. Krantz (2011), The Proof Is in the Pudding: The Changing Nature of Mathematical Proof, Springer, ISBN 0387489088, p. 92.
  3. ^ Donald Ervin Knuth (1984), The TeXbook, Addison-Wesley, ISBN 0201134489.
  4. ^ Frank Mittelbach, Michel Goossens, Johannes Braams, David Carlisle, Chris Rowley, Christine Detig, and Joachim Schrod (2004), The LaTeX Companion, Chapter 3: Basic Formatting Tools, Addison-Wesley.

See also

External links